Process for producing resonant tag

ABSTRACT

A process for producing a resonant tag, wherein a metal foil having a thermal adhesion adhesive applied to at least one face thereof is stamped out into a circuit-like shape and is adhered to a base sheet, the process comprising: stamping out the metal foil into a predetermined shaped metal foil portion ( 4   c ) while being passed through a die roll ( 1 ) having thereon a stamping blade with a predetermined shape and a transfer roll ( 2 ) in contact with the die roll ( 1 ) which functions also as a die back-up roll; holding this metal foil portion obtained by the stamping-out operation onto the surface of the transfer roll by suction holes formed in the transfer roll; and thermally adhering the stamped metal foil portion to the base sheet ( 7 ) in contact with the transfer roll ( 2 ) at its another face by an adhesive roll ( 3 ) in contact with the transfer roll through the base sheet. The present invention has such advantages as no damage to the base sheet since the stamping-out operation for the metal foil and the thermal adhesion operation thereof to the base sheet are carried out in separate positions, and no requirement of carrier sheet because the resultant metal foil portion obtained by the stamping-out operation is sucked and held onto the surface of the transfer roll.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a process for producing aresonant tag equipped with a resonant frequency circuit which resonateswith a radio wave transmitted at a particular frequency from a detector.

[0003] 2. Description of the Related Art

[0004] As is well known, resonant tag is a tag equipped with a resonantcircuit which resonates with a radio wave transmitted at a particularfrequency. Thus, when the resonant tag is brought into an area in whichthe radio wave of the particular frequency is transmitted, the resonanttag readily reacts to operate a buzzer or an alert lamp of a detector.Thus, to avoid shoplifting, the resonant tags are attached to goods andthe like in department stores, discount stores, rental shops for videotapes, compact disk (CD) shops, etc.

[0005] Basically, a resonant tag is composed of a plastic film (as adielectric), having a spiral (or a coil-shaped) circuit (hereinafterreferred to as a “coil circuit”) on at least one face of the film, and acircuit for use as an electrode plate of a capacitor or another coilcircuit which functions also as a capacitor on the other face of thefilm. If necessary, the resonant tag is laminated on a sheet of a basematerial such as a paper.

[0006] In addition to a resonant tag above, there is also proposed aresonant tag having no capacitor electrode section formed on the endportion of the coil circuit. In the proposed structure, coil circuitsare formed on both faces of a plastic film in correspondence with eachother to utilize the circuit itself as the capacitor electrode plate.

[0007] The following processes have been known as processes forproducing a resonant tag and the like. In one process, the followingsteps are carried out. A metal foil such as an aluminum foil islaminated on a plastic film. A photosensitive resin is applied to a faceof this metal foil. A negative film-having a predetermined circuitpattern is placed on the resin-coated face and is photosensitized.Non-photosensitive portion is developed and removed, and the exposedmetal foil is then etched and removed, to form a circuit. In anotherprocess, the following steps are carried out. A metal foil is stampedout by a die stamp having a blade with a predetermined shape, to form acircuit, and the metal foil is thermally adhered to a base sheet (asheet of abase material) at the same time when the stamping isconducted.

[0008] The present invention relates to an improvement of die stampingin the foregoing processes.

[0009] In the die stamping process, die must stamp out a metal foil thatis formed into a roll while tine metal foil being rewound, and thermallyadhere the metal foil to a base material, for the continuous working.Thus, the die stamping is applicable to laminate a metal foil withstrength to some degree on a solid base material, whereas the diestamping is not so advantageous for other cases. Therefore, the diestamping is suitable for a printed circuit board using a relativelythick copper foil and including a phenol resin plate as a base material,etc.

[0010] A resonant tag is basically disposable and formed into a thinlabel, so that the resonant tag mainly adopts a reasonable thin aluminumfoil as a metal foil, and a soft plastic film or paper as a base sheet.Thus, that aluminum foil may be broken or the base sheet may be alsostamped out during stamping out or transferring the foil, so that theresonant tag using the die stamping has not been put into practical usein the current state.

[0011] In order to solve these problems, such a process is attemptedthat a metal foil is laminated on a carrier sheet which has thickthickness and a stamping die only stamps out the metal foil to transferthis metal foil onto a plastic film (as a dielectric) or a base sheet.However, this process has such problems as (1) the additional step oflaminating the metal foil on the carrier sheet is required; (2) themetal foil and the carrier sheet must be separated with difficulty; (3)when the stamped-out shape is discontinuous such as round, theseparation between the stamped-out portion and the non stamped-outportion is difficult; and the like.

SUMMARY OF THE INVENTION

[0012] The present invention is intended to provide a process forcontinuously producing a resonant tag using the die stamping.

[0013] The present invention will be described taking a resonant tag asan example. However, of course, the present invention is not to belimited to the resonant tag, but can be applied to a production of goodssimilar thereto.

[0014] The present invention provides a process for producing a resonanttag, wherein a metal foil having a thermal adhesion adhesive applied toat least one face thereof is stamped out into a circuit-like shape andis adhered to a base sheet, the process comprising: stamping out themetal foil into a predetermined shaped metal foil portion while beingpassed through a die roll having, at its roll face, a stamping bladewith a predetermined shape and a transfer roll in contact with the dieroll which functions also as a die bearing roll or back-up roll; holdingthe resultant metal foil portion obtained by the stamping-out operationonto the surface of the transfer roll by suction holes formed in thetransfer roll; and thermally adhering the metal foil portion obtained bythe stamping-out operation to the base sheet in contact with thetransfer roll at its another face (i.e., another face of the transferroll) by an adhesive roll in contact with the transfer roll through thebase sheet.

[0015] Further, according to the present invention, in theabove-described process, as the adhesive roll is used an adhesive rollhaving protrusions thereon so as to correspond in shape to metal foilportions obtained by the stamping-out operation which is to betransferred.

[0016] Still further, according to the present invention, theabove-described process is characterized in that a second transfer rollhaving protrusions thereon is provided between the transfer roll and theadhesive roll so as to correspond in shape to metal foil portionsobtained by the stamping-out operation which is to be transferred, andthe resultant metal foil portions obtained by the stamped-out operationare transferred from the transfer roll to the protrusions on the secondtransfer roll, and is then thermally adhered to the base sheet runningbetween the second transfer roll and the adhesive roll. In this process,the second transfer roll is formed with suction holes to hold the metalfoil as is the case of the first transfer roll.

[0017] Still further, the present invention intends to provide resonanttags which can be readily manufactured and which have stable resonantcharacteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the accompanying drawings,

[0019]FIG. 1 is a schematic view showing a process for illustrating oneembodiment of the present invention;

[0020]FIG. 2 is a schematic view showing a process for illustratinganother embodiment of the present invention;

[0021]FIG. 3 is a schematic view showing a process for illustratingstill another embodiment of the present invention;

[0022]FIGS. 4A to 4D are perspective views showing an example in thestructure of a resonant tag; and

[0023]FIG. 5 is a top plan view showing an example of an arrangement ofsuction holes provided on a roll surface.

[0024]FIG. 6 is an exploded perspective view showing one example of thepresent invention.

[0025]FIG. 7A and FIG. 7B are plan views showing the surface and backface of one example of the conventional resonant tag.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A metal foil used in the present invention is to be thermallyadhered to a base sheet after being stamped out into a predeterminedshape. Basically, a metal foil is used where an adhesive having thermaladhesive property (hereinafter referred to as a “thermal adhesionadhesive”) is applied to at least one face of the foil. Such a commonlyknown thermally adhesive resin can be used as the thermal adhesionadhesive including vinyl chloride resin, vinyl acetate resin and acrylicresin.

[0027] The thickness of the thermal adhesion adhesive to be applied isnot particularly limited, but is generally about 1 to 3μ(micron),preferably about 1 to 2μ. The thermal adhesion adhesive can alsofunction to reinforce the metal foil.

[0028] Surface-coating may be applied to the other face of the metalfoil by using resin, if necessary. The resin and the like to be appliedthereto can be the one for simply protecting a surface, or the one forfacilitating further processes. Otherwise, a thermal adhesive coatingand the like having higher temperature thermal adhesion than that of theabove thermal adhesion adhesive may be provided.

[0029] The metal foil having a thickness to the extent that it may notbe broken with tension exerted on the metal foil is generally used inthis process. However, a thinner metal foil can also be used togetherwith a carrier sheet. In this case, the carrier sheet is not adheredwith the metal foil but is simply placed thereon. The carrier sheet isthen stamped out together with the foil. The force sucking from thesuction holes formed in the transfer roll is acted on the metal foilthrough this sheet, so that the carrier sheet and the metal foil areboth held onto the surface of the transfer roll. Accordingly, thecarrier sheet is desirably a paper having air-permeability. After themetal foil has been adhered with the base sheet, this carrier sheet maybe advantageously removed in a manner such as blow-off with air.

[0030] The metal foil having a thickness of about 50μ is preferable inview of workability, more preferably 20-60μ, specifically 30-50μ.

[0031] According to the present invention, the transfer roll serves as adie back-up roll when the die roll stamps out the metal foil. Thetransfer roll also serves to hold the stamped metal foil portionsthereto and to adhere the stamped metal foil portions to the base sheetin contact with the transfer roll at its another face. According to thepresent invention, to hold the stamped metal foil portions onto the faceof the roll, a large number of suction holes are formed in the transferroll corresponding in shape to the stamped metal foil portions. Then,the stamped foil portions will be sucked and held by the force suckingfrom these holes.

[0032] Since the surface of the transfer roll serves to bear the dieblade, it is advantageously formed with resilient layers such as layersmade of synthetic rubber such as polyurethane or plastic layers. Thelayers are preferably fluorine plastic layers or the like having heatresistance, low heat conductivity, and excellent peeling-off property tomeet such conditions as an ability of resisting heat when the metal foilis thermally adhered to the base sheet, an ability of not transferringheat to the roll itself from the adhesive roll, and an ability ofpeeling off the roll from the metal foil.

[0033] The suction operation from the suction holes in the transfer rollmay be carried out in such a manner that an air is always sucked frominside of the roll, without any use of special structure, or with anyuse of special structure.

[0034] The suction holes at the face where the metal foil is not heldduring the use of the transfer roll may be closed with any member in asliding contact with the outer surface of the roll. Alternatively, apartition or the like is formed within the transfer roll so that nosuction force can act on the suction holes. A built-in valve set in sucha manner that the holes are closed when the sucking force strongly actson the suction holes may be provided.

[0035] The adhesive roll is used to thermally adhere the stamped metalfoil portions to the base sheet. The thermal adhesion may be carried outin either way. That is, while the adhesive roll itself is used as a heatroll, the foil portions are adhered with heat of this roll. As anotherway, the foil portions are adhered by pressing between the transfer rolland the adhesive roll with a hot air being blown to the metal foil orwith the metal foil being heated with an infrared lamp, etc.

[0036] When the stamped metal foil portions is adhered to a flat basesheet, an adhesive roll having no irregularity thereon is normally used.

[0037] When the metal foil is thermally adhered by heat of the adhesiveroll, sometimes, the transfer roll is heated due to heat transfer fromthe adhesive roll, prohibiting the foil from being stamped out. In orderto avoid this, advantageously, the adhesive roll formed thereon withprotrusions so as to correspond in shape to the stamped metal foilportions is used to thermally adhere the metal foil at the protrusionsthrough the base sheet.

[0038] The adhesive roll is normally made of metal, but the adhesiveroll having the protrusions at which metal is exhibited and theremainder surface lined with heat-resistant rubber, etc. to reduce theirregularity may also be used. In this connection, the heat-resistantrubber, etc. may be the one that is compressed when the roll is pressed.

[0039] Like the stamped foil portions, the protrusions formed on theroll may be of a spiral shape with a slightly wider width when thestamped foil portion is of a square shape. It can also be square so asto include this spiral shape.

[0040] If a base sheet to which a circuit-like metal foil has beenalready adhered is used to adhere a second circuit-like metal foil ontothe face of the first circuit-like metal foil, the roll having a flatsurface such as the transfer roll and/or the adhesive roll sometimesdoes not contribute to good adhesion.

[0041] In order to overcome such circumstances, a roll havingprotrusions thereon is advantageously used for the transfer roll and/orthe adhesive roll. The protrusion transfer roll can have a similarstructure to that of the protrusion adhesive roll as described above,except that suction holes are formed therein.

[0042] The protrusion transfer roll is often troublesome to be used as adie back-up roll for the die roll in that the stamping die and theprotrusions must be aligned with each other, etc. Therefore, it can beused, in addition to a first transfer roll which functions also as a dieback-up roll, as a second transfer roll in contact with the firsttransfer roll. The second transfer roll is also formed therein withsuction holes like the first transfer roll.

[0043] As is apparent from the foregoing description, according to thepresent invention, the metal foil that has been stamped out by the dieroll is sucked and held to the transfer roll to be thermally adhered tothe base sheet in contact with the transfer roll at its another face.This structure has a large number of advantages such as no damage to thebase sheet, and no requirement of expensive carrier sheet. Besides, thestamped metal foil portions can be individually sucked and held to thetransfer roll in an independent manner, so that no specific attentionmust be paid to the shape of the stamped-out portions.

[0044] As shown in FIGS. 4A to 4D, according to the present invention,in particular, a resonant tag A formed in such a manner that twocoil-shaped metal foils 41, 42 are adhered with each other by thermaladhesion adhesive (thermal adhesive) layers 51, 52 which function alsoas dielectric layers can be readily fabricated without any use ofdielectric sheet. The thermal adhesive layers 51, 52 are in advanceapplied to the metal foils 41, 42, and the metal foils 41, 42 arcadhered with each other by thermal adhesion, to form a resonant circuitwhile the both metal foils are electrically conductive in part. In FIG.4D, reference numeral 43 indicates a conductive section.

[0045]FIG. 4A shows coil-shaped metal foils made by applying the thermaladhesion adhesive to the metal foils 41, 42, as indicated by referencesymbols 4 c ₁, and 4 c ₂. FIG. 4B is an exploded perspective view ofFIG. 4A. FIG. 4C shows the state where the coil-shaped metal foils 4 c₁, 4 c ₂ arc adhered with each other. FIG. 4D particularly shows theconductive section 43.

[0046] It will be understood that the base sheet used in the presentinvention is in general formed of a paper used for a tag or label, butcan be also formed of a plastic film (as a dielectric) or aresin-impregnated paper.

[0047] Preferred embodiments of the present invention will behereinafter described with reference to the accompanying drawings.However, the present invention should not be limited to theseembodiments.

[0048]FIG. 1 shows an embodiment of the principle process of the presentinvention. Reference numeral 1 denotes a die roll, reference numeral 2does a transfer roll, and reference numeral 3 does an adhesive roll. Inpractical use, a metal foil 4 a having thermally adhesive resin appliedthereto is rewound from a rolled foil 4 that is wound with the foil. Themetal foil is then fed between the die roll 1 and the transfer roll 2through a guide roll 5, where it is stamped out into a predeterminedshape. Stamped metal foil portions 4 c are held onto the surface of thetransfer roll 2 by suction holes (not shown) formed in the roll 2, andthen adhered to a base sheet 7 running on the adhesive roll 3 in contactwith the lower face of the transfer roll 2 in position.

[0049] In the present embodiment, the transfer roll 2 and the adhesiveroll 3 both have smooth roll faces. The adhesive roll 3 is a metal heatroll (a heating roll).

[0050] Unnecessary metal foil portion 4 b after the foil has beenstamped out by the die roll 1 is ejected by a vacuum air to outside ofthe system through a discharging duct 8. In this figure, referencenumeral 9 denotes a vacuum duct for sucking and removing fine pieces andthe like that may be produced during the stamping-out operation.

[0051]FIG. 2 shows another embodiment of the present invention in whicha protrusion adhesive roll 3A is employed instead of the adhesive roll 3described in the previous embodiment shown in FIG. 1. Other structuresare the same as those shown in FIG. 1.

[0052] According to this modification, in the case where the adhesiveroll is a heating roll, an unsuccessful stamping-out operation for thefoil 4 a which is caused by the fact that heat is transferred to thetransfer roll 2 and the die roll 1 is also heated can be prevented.Besides, the roll having the protrusions thereon may ensure a pressingforce during the adhesion. Therefore, it is suitable to adhere thestamped foil portions 4 c in this step to that metal foil on the basesheet which has been already adhered with the previously stamped foilportions.

[0053]FIG. 5 shows an example of an arrangement of suction holes formedin the transfer roll and protrusions formed on the protrusion roll. FIG.5 is a partial developed view showing the roll. In this figure, brokenline 31 indicates a contour of the metal foil to be stamped out, and anappropriate number of suction holes 32 are formed inside surrounded bythe broken line 31. The protrusions each having slightly wider than thespiral (or coil) shape indicated by the broken line 31 may be spirallyformed on the surface of the transfer roll or the adhesive roll. Theprotrusions may be formed into a square shape so as to include thisspiral shape.

[0054]FIG. 3 shows another embodiment of the present invention in whicha protrusion transfer roll 2A is inserted between the transfer roll 2and the adhesive roll 3. Other structures are the same as those shown inFIG. 1, so that identical reference numerals are given, an explanationbeing omitted on the remaining members.

[0055] According the present embodiment, by a provision of a secondtransfer roll 2A having protrusions thereon, heat from the adhesive roll3 is hardly further conducted to the transfer roll 2 and the die roll 1.In addition, the stamped foil portions 4 c can be surely adhered to thebase sheet 7 having irregularity, as is the case of FIG. 2.

[0056] In this embodiment, if necessary, the protrusion adhesive roll 3Ashown in FIG. 2 can also be used. Incidentally, reference numeral 10indicates a hot-air ejection nozzle for preliminarily heating the basesheet 7 and the adhesive roll 3. The preliminary heating with the hotair will be particularly useful for the roll 3 to thermally adhere themetal foil previously adhered to the base sheet. This exhibits such aneffect as an improvement of productivity.

[0057] The relationship of a capacitance (C), an inductance (L) andresonant frequency (f) in the resonant circuit is shown by the followingformula (I).

L=1/(4π² f ² C)  (I)

[0058] L is an inductance in a circuit-like coil and the shape of thecircuit-like coil is dependent on the resonant frequency f. As derivedfrom the formula (I), the resonant frequency f is in inverse proportionto a square root of the product of the capacitance (C) and theinductance (L) and therefore, it is required to make the inductance (L)great so as to make the resonant frequency f small. In general,inductance (L) in a circuit-like coil has been dependent on the numberof winding the circuit-like coil and the outer dimension of thecircuit-coil. Thus, it has been considered that the more the number ofwinding the coil is much and the more the diameter of the coil is large,the more an inductance which is great can be obtained. For this reason,a desired resonant frequency has been obtained by increasing the numberof winding a circuit-like coil.

[0059] In the conventional resonant tag, for example, as shown in FIG.7A, a circuit-like coil 44 in which the line width of the coil and thedistance between neighboring lines of the coil are made thin in a narrowarea is provided so as to surround a capacitor portion 45 a. FIG. 7Ashows a face (surface) on which the circuit-like coil 44 of the resonanttag is provided. FIG. 7B shows a reverse face of the surface shown inFIG. 7A. In FIGS. 7A and 7B, reference numeral 54 shows a plastic film,reference numeral 47 shows a circuit for the capacitor, referencenumeral 46 shows a circuit-connecting terminal area and referencenumerals 45 a and 45 b show the capacitor portion.

[0060] The plastic film 54 takes roles of a substrate on which thecircuit like coil 44 is provided and of a dielectric by positioningbetween the capacitor 45 a at the surface and the capacitor 45 b at thereverse face. The circuit-like coil 44 at the surface of the plasticfilm 54 and the circuit 47 for the capacitor 45 b on the both faces ofthe plastic film 54 are connected by the circuit-connecting terminalarea 46, whereby forming a resonant circuit.

[0061] As explained above, the conventional resonant tag is providedwith circuit-like coil which has great number of winding on one face(surface) of a dielectric film.

[0062] In the conventional resonant tag, in a case that resonantfrequency is 8.2 MHz and the size of the tag is 40×40 mm, the averageline-width of a circuit like coil to the length of the most outerperiphery of the circuit-like coil is 1/150 or less of said length andthe number of winding the coil is made round about seven times.

[0063] The circuit like coil is normally formed by a method for etchinga metal foil such as aluminum foil, copper foil, etc. or a Method forapplying an electrically conductive coating containing metal powder ofthese aluminum, copper, etc. In these methods, however, there have beencases that when the thickness (line width) of a circuit-like coil isthin or when the distances between the neighboring lines becomes narrow,the lines are burnout or the lines are connected to each other at themanufacturing step or the lines connected to each other, resulting inproducing inferior circuits. These defects have been also generated atthe secondary processing step after the formation of the circuit andtherefore, much cares have been necessary in obtaining resonant tagshaving stable resonant characteristics.

[0064] In order to solve the above-described defects, the presentinvention provides the resonant tags which can be readily manufacturedand which have stable resonant characteristics.

[0065] The resonant tags of the present invention are characterized inthat at least two circuit-like coils in which the line-width of eachcircuit is 1/50 or more to the length of the most outer periphery ofeach circuit and the number of winding the coil is made round threetimes or less are provided on the both faces of a dielectric film insuch a manner that the both circuit-like coils are faced to each other.

[0066] In the present invention, the circuit-like coil may be formed byusing a metal foil such as aluminum foil, copper foil, etc. or may beformed by the application of an electrically conductive coatingcontaining these metal powder. It is preferable to form the circuit-likecoil by using metal foils.

[0067] By adhering the circuit-like coils on the both faces of thedielectric film so as to be faced to each other, a capacitor is formedby a portion at which the both circuit-like coils are faced to eachother by sandwiching the dielectric film. Said capacitor takes a role ofa capacitor which is provided in the conventional resonant tag. By theconstitution of the resonant tag according to the present invention,there is no necessity of separately providing a capacitor portion at theterminal or the center of the coil.

[0068] As the dielectric film, plastic films, resin films or coatedresin film may be used. The two circuit-like coils which are to beadhered on the both faces of the dielectric film are adhered in such amanner that the directions where the coils are wound are different toeach other, and the circuit-like coils at the both faces of thedielectric film are connected at the circuit-connecting terminal areawhich is positioned at the ends of the coils, whereby forming a resonantcircuit. (see FIG. 4D).

[0069] As an index which shows a performance of the resonant circuit, Qvalue (strength of resonance) is used. The Q value is shown by thefollowing formula (II).

Q=2πfL/R  (II)

[0070] In the formula (II), R represents a resistance value, frepresents a resonant frequency and L represents an inductance.

[0071] It has been popular view that the more resonant circuits havehigh Q value, the more such resonant circuits are excellent. In a casethat the resonant circuits having higher Q value is used in datacommunication, electric supply and existence-recognition in whichresonant phenomenon is utilized, system having high efficiency and highenvironmental resistance can be performed.

[0072] By making the thickness of the coil portion (line width of thecoil) thick, it is possible to keep the resistance value of the lineroots low. Further, the length of the coil becomes short and therefore,the resistance value at the portions of the coil can be made low.

[0073] In the conventional one-face coil in which the coil-extension isthin and long, it has been required to use a copper foil or gold-platedcopper foil which has high conductivity (low resistance value) so as toform a resonant circuit having high performance. By the techniques ofthe present invention, it becomes possible to use a metal foil such asaluminum foil, etc. which is not expensive and has good workabilitywhile retaining the performance and to use thin metal foils. Moreover,since the thickness of the line width of the coil is thick, the methodof producing the resonant tags of the present invention, i.e., a methodfor stamping out the metal foil into a coil-form and a method forsuctioning and transferring the stamped metal foil can be readilycarried out.

[0074] In a case of the both-face coils according to the presentinvention, the inductance L is reduced by shortening the length of thecoil. On the other hand, since the line-width of the coil becomes thick,the resistance value R is reduced.

[0075] As a result, it is possible to retain or increase the Q valueaccording to the structure of the both-face coils in which the reducingratio of R is larger in comparison with the reduction ratio of L.

EXAMPLE AND COMPARATIVE EXAMPLE

[0076] Size of resonant tag: 40×40 mm (dimension which becomes an outerperiphery of the circuit)

[0077] Resonant frequency: 8.2 MHz

[0078] Under the above-mentioned conditions, the resonant tag of thepresent invention (Example) and the conventional resonant tag weremanufactured and the performances of the manufactured resonant tags werecompared.

[0079] The resonant tag of the Example is a resonant tag of theboth-face coil type as shown in FIG. 4D. The Comparative Example is aresonant tag in one-face coil type as shown in FIG. 7.

[0080] The constitutions and properties arc shown in Table 1. TABLE 1Comparative Example Example Coil material aluminum foil aluminum foilthickness (surface/back)  50 μm/10 μm  40 μm/40 μm number of winding  82/1 (surface/back) Dielectric capacitor  20 μmPE film  3 μm coated resinfilm area/volume 121 mm²/123 pF 727.3 mm²/4937 pF L (inductance)  3.06μH  0.154 μH Length of coil 980 mm 284 mm Coil resistance  0.6860 Ω 0.03976 Q Q calculated value 230 199 found value  58  60

[0081] As shown in Table 1, the resonant tag of the present inventionhas the similar resonant strength to that of the conventional resonanttag in spite that the number of winding coil is less.

[0082]FIG. 6 is an exploded perspective view showing the constitution ofthe other Example of the resonant tag according to the presentinvention. The coil-shaped metal foils 4C₁, 4C₂ which are stamped out bythe method of the present invention are adhered to the both faces of adielectric sheet 53 and then, they are adhered to a base sheet 71.

[0083] In the constitution of FIG. 6, when thermal adhesive film such aspolyethylene film is used as the dielectric sheet 53, the metal foils41, 42 in coil-shape in which a thermal adhesion adhesive is not coatedcan be used. As the base sheet 71, a thick paper, paper board, etc. theface of which is provided with beautiful printing can be used.

[0084] The resonant circuit of the present invention take a role of theconventional capacitor by connecting the lines of the coils at thesurface and back face. On top of this role, since the line width of thecoil is thick, the volume of capacitor can be easily adjusted andresonant frequency can be changed by slightly moving the connected faceof the coils at the both faces or by changing the size of the conductivesection 43 as shown in FIG. 4.

[0085] Although the present invention is explained by mainly referringto the resonant tag, it can be used as IC tag or IC card by theincorporation of IC chip.

[0086] Although the IC chip has a specific capacitance, each chip hasvariance in capacitance. This variance renders the resonant frequency ofIC tag or TC card to be varied when the IC chip is provided in theresonant circuit.

[0087] As apparent from the Table 1, the Comparative Example obtainsresonant frequency by a small volume (123 pF) with respect to a large L(inductance) and therefore, the variance of capacitance of IC chiprenders the variance of the resonant frequency of IC tag or IC card tobe large.

[0088] On the other hand, since the Example of the present inventionobtains resonant frequency by a large volume (4937 pF) with respect to asmall L, influence of the variance of capacity of IC chip to theresonant frequency of IC tag or IC card is very less. This means thatvariance of the resonant frequency of IC tag or IC card which uses theresonant circuit of the present invention is very less,

[0089] In a case that IC chip is mounted in the resonant circuit, it isconsidered that the matching of the resonant circuit and IC chip is veryimportant in a viewpoint of performance. Since the adjustment of thecapacitance and inductance in the resonant circuit of the presentinvention is readily made, the impedance of the resonant circuit can beeasily adjusted and the matching of the resonant circuit and IC chip ismade with facility.

[0090] In the conventional resonant tag, it has been required to adjustresonant frequency by lowering the capacity volume by cutting a part ofa circuit after IC chip is provided. However, the circuit of the presentinvention does not require such adjustment or adjustment is possiblewithout conducting the adjustment in the conventional resonant tag.

What is claimed is:
 1. A process for producing a resonant tag, wherein ametal foil having a thermal adhesion adhesive applied to at least oneface thereof is stamped out into a circuit-like shape and is adhered toa base sheet, said process comprising: stamping out the metal foil intoa predetermined shaped metal foil portion while being passed through adie roll having thereon a stamping blade with a predetermined shape anda transfer roll in contact with the die roll which functions also as adie back-up roll; holding the resultant metal foil portion obtained bythe stamping-out operation onto the surface of the transfer roll bysuction holes formed in the transfer roll; and thermally adhering themetal foil portion obtained by the stamping-out operation to the basesheet in contact with the transfer roll at its another face by anadhesive roll in contact with the transfer roll through the base sheet.2. A process for producing a resonant tag as claimed in claim 1, whereinthe adhesive roll is an adhesive roll having protrusions thereon so asto correspond in shape to metal foil portions obtained by thestamping-out operation which is to be transferred.
 3. A process forproducing a resonant tag, wherein a metal foil having a thermal adhesionadhesive applied to at least one face thereof is stamped out into acircuit-like shape and is adhered to a base sheet, said processcomprising: stamping out the metal foil into a predetermined shapedmetal foil portion while being passed through a die roll having thereona stamping blade with a predetermined shape and a transfer roll incontact with the die roll which functions also as a die back-up roll;holding the resultant metal foil portion obtained by the stamping-outoperation onto the surface of the transfer roll by suction holes formedin the transfer roll; transferring the metal foil portion obtained bythe stamping-out operation onto a second transfer roll in contact withthe transfer roll, the second transfer roll being formed therein withprotrusions and suction holes so as to correspond in shape to metal foilportions obtained by the stamping-out operation; and thermally adheringthe metal foil portion obtained by the stamping-out operation to thebase sheet running between the second transfer roll and the adhesiveroll.
 4. An apparatus for producing a resonant tag comprising: a dieroll having thereon a stamping blade with a predetermined shape; atransfer roll functioning also as a die back-up roll in contact withsaid die roll; and an adhesive roll for thermally adhesion in contactwith said transfer roll at its another face, wherein an appropriatenumber of suction holes are formed in said transfer roll so as tocorrespond in shape to metal foil portions obtained by the stamping-outoperation to hold the stamped metal foil portions onto the roll.
 5. Anapparatus for producing a resonant tag as claimed in claim 4, whereinthe adhesive roll is an adhesive roll having protrusions thereon so asto correspond in shape to metal foil portions obtained by thestamping-out operation which is to be transferred.
 6. An apparatus forproducing a resonant tag comprising: a die roll having thereon astamping blade with a predetermined shape; a transfer roll functioningalso as a die back-up roll in contact with said die roll; a protrusiontransfer roll in contact with said transfer roll; and an adhesive rollfor thermal adhesion, wherein as appropriate number of suction holes areformed in said transfer roll and said protrusion transfer roll so as tocorrespond in shape to metal foil portions obtained by the stamping-outoperation to hold the stamped metal foil portion onto the rolls, andprotrusions are formed on said protrusion transfer roll so as tocorrespond in shape to the stamped metal foil portions to betransferred.
 7. A resonant circuit characterized in that at least twocircuit-like coils in which the line-width of each circuit is 1/50 ormore to the length of the most outer periphery of each circuit and thenumber of winding the coil is made round three times or less areprovided on the both faces of a dielectric film in such a manner thatthe both circuit-like coils are faced to each other.
 8. A resonantcircuit as claimed in claim 7, wherein the circuit-like coil comprisesof a meal foil such as aluminum foil, copper foil, etc. and the circuitlike coils are adhered to a dielectric film.
 9. A resonant circuit asclaimed in claim 7 or 8, wherein the winding direction of the twocircuit-like coils which are to be adhered on the both faces of thedielectric film are in different directions to each other.
 10. Aresonant circuit as claimed in claim 7, wherein the dielectric filmcomprises of plastic film, resin film or resin coating.
 11. A resonantcircuit as claimed in claimed in claims 7 to 10, wherein the dielectricfilm is provided only on the circuit-like coil.
 12. A resonant tagprovided with a resonant circuit as described in any one of claims 7 to11.
 13. An IC tag or an IC card provided with a resonant circuit asdescribed in any one of the claims 7 to 11.